Electrical apparatus for generating current pulses



p 27, 1966 L. H. SEGALL ETAL 3,275,884

ELECTRICAL APPARATUS FCR GENERATING CURRENT PULSES Filed Sept. 21, 1961 5 Sheets-Sheet l SQUW INVENTORS LOUIS H. SEGALL 2 N BY JAMES c MORRISON JAMES KNAK ATTOR EYS P 1966 L. H. SEGALL ETAL. 3,275,884

ELECTRICAL APPARATUS FOR GENERATING CURRENT PULSES Filed Sept. 21 1961 3 Sheets-Sheet 3 INVENTORS LOUIS H. SEGALL JAMES c. MORRISON BY JAMES KNAK wwgz m ATTOR Y8 United States Patent 3,275,884 ELECTRICAL APPARATUS FOR GENERATING CURRENT PULSES Louis H. Segall, James C. Morrison, and James Knak,

all of Sidney, N.Y., assignors to The Bendix Corporation, Sidney, N.Y., a corporation of Delaware Filed Sept. 21, 1961, Ser. No. 139,713 14 Claims. (Cl. 315-163) This invention relates to electrical apparatus, and more particularly relates to a system for firing ordnance devices and the like. Typical of the devices with which the firing system of the invention may be used to advantage are devices employing exploding bridge wire squibs, and primers.

The invention has among its objects the provision of a novel firing system of the type indicated, wherein the design of the system is such as to allow it tobe located close to its related ordnance device, thereby eliminating long high energy output cables.

A further object of the invention is the provision of a firing circuit system which permits the elimination of high voltage interstage connectors.

A still further object of the invention is the provision of a novel, simplified pulse generator which may be employed to advantage in the arming circuit or power source for the firing system of the invention.

Another object of the invention, and preferred embodiments thereof, is the provision of a firing system wherein a plurality of trigger circuits, each adapted to fire its respective exploding bridge wire device, is associated with a single arming circuit, thereby effecting a considerable reduction in the weight and volume of the system.

Yet another object of the invention is the provision of a firing system wherein the main operating elements thereof are provided in multiple with the exception of a common power supply and a filter for the power supply.

Still another object of the invention is the provision of a multiple firing circuit, including a plurality of trigger circuits, each operated by its respective triggering signal.

Other objects of the invention include the provision of a multiple firing system having a plurality of sections, each with its own power supply, the system being so designed that if for any reason one section of the power supply should open or become short circuited, the remaining section would continue to operate, and the provision of a firing system of the type indicated, wherein the exploding bridge wire device is protected against misfiring as a result of circulating ground currents.

The above and further objects and novel features of the invention will more fully appear from the following description when the same is read in connection with the accompanying drawings. It is to be expressly understood, however, that the drawings are for the purpose of illustration only, and are not intended as a definition of the limits of the invention.

In the drawings, wherein like reference characters refer to like parts throng-ht the several views,

FIG. 1 is a circuit diagram of a first illustrative embodiment of dual firing system in accordance with the invention;

FIG. 2 is a wiring diagram of a second embodiment of firing system in accordance with the invention; and

FIG. 3 is a wiring diagram of a third embodiment of firing system in accordance with the invention.

The electrical system of the invention may be called a high energy initiation firing set. Such circuit or set includes a high voltage electronic power supply which provides an output pulse of sufficient energy to allow the reliable operation of exploding bridge wire ordnance devices. Among such devices are squibs for the separation of the various stages of a missile and for the initiation "ice of the functions of succeeding stages. In the Pershing missile, for example, which has three stages in addition to the warhead unit, there are employed fourteen such squibs. In the application of the firing circuit of the present invention to such missile, each firing unit is located very close to its related ordance device, thereby eliminating problems which would otherwise occur with long high energy cables. The ordnance items are each provided with two exploding bridge wire devices for complete ordnance control duplication or redundancy. This arrangement, coupled with the provision of individual initiation units, provides two completely independent firing sets, either of which could perform the intended initiation functions.

The firing circuit or set of the present invention includes an arming circuit which includes a source of power and a storage condenser charged thereby. The circuit further includes a trigger circuit which detects the firing signal, and then supplies a signal for the initiation of events which result in the discharge of the storage condenser of the arming circuit. The energy thus discharged from the storage condenser flows to and operates the exploding bridge wire device.

In the three embodiments of firing circuit or set specifically disclosed herein, there is employed a dual unit wherein one arming circuit is associated with two trigger circuits. 'It has been found that with such arrangement there is a marked reduction in the weight of the circuit devices required and in the volume requirements of the circuit over an arrangement wherein each trigger circuit has a separate arming circuit associated therewith. Each trigger and discharge section of the dual unit is independent of the other and may, if desired, be externally programmed to fire at different time intervals. In preferred installations of the circuit of the invention in a missile, for example, two explosive bridge wire devices of each ordnance item are served by two different dual units. With this arrangement, no ordnance function is totally dependent on any one dual unit. Therefore, complete redundancy is present throughout the system.

Turning now to FIG. 1 of the drawings, there is shown a first embodiment of firing circuit in accordance with the invention. The portion of the circuit shown at the top of the figure and generally designated by the reference character 10 includes the power supply and the arming circuit of the system there shown. The two trigger circuits associated with the arming circuit are designated 68 and 68; the two trigger circuits are identical, and so the parts of circuit 68 are designated by the same reference characters as those in circuit 68 but with an added prime.

A source of direct current power such as a battery is connected to the positive terminal 11 and to the negative terminal 12 of the arming circuit. Terminal 12 is grounded, as shown. Terminal 11 is connected by wire 13 to a radio interference filter 14 having a choke coil 15 connected to the input wire 13 and an output wire 19. A condenser 16 is connected across wire 13, in advance of coil 14, and ground and another condenser 17 is con nected across wire 19 to ground. Interposed in output wire 19 from the filter is a power resistor 20, the primary function of which is to prevent short circuiting of the direct current input connected to terminals 11 and 12 in the event of failure of transistor 29' in the pulse generating section of the arming circuit.

The pulse generating section of the arming circuit transforms the steady direct current of the current source to a succession of pulses which are rectified and which serve to charge the two storage condensers 57 and 57 of the arming circuit. The output end of resistor 20 is connected to one end of a coil 21 which forms the primary winding of a power transformer 22. In the illustrative circuit, transformer 22 is of such design as to step up the input voltage from 27 volts to 2,000 volts. The primary 21 of the transformer 22 is wound as an autotransformer, there being a lower portion 24 of primary 21, connected to an oscillator through wires 25 and 32, and an upper, serially connected portion 23. Wire 25 is connected to the base 27 of a transistor 29. A resistor 26 is interposed in wire 25 as shown. A wire 30 having a resistor 31 interposed therein extends from the base 27 of the transistor to ground. Resistor 26 is employed to match the oscillator circuit to the transformer winding. Wire 32, which has a resistor 34 interposed therein, is connected to the emitter 35 of the transistor 29. Resistor 34 is used for temperature stabilization of the oscillator circuit. The collector 36 of the transistor 29 is connected to ground through wire 37. Transformer 22 has a core 39 and a secondary winding 41, the primary and secondary windings being magnetically linked with the core.

The above described pulse generator functions as follows: When voltage appears across the emitter 35 and collector 36 of the transistor 29, a small current flows from the emitter 35 to the base 27 through resistor 31. This current, which can be termed a starting current, causes the transistor 29 to conduct enough initial current to cause voltage to be induced across the base 27 and emitter 35 due to the autotransformer action of the primary winding 21 of transformer 22. This feedback or induced voltage is of such polarity as to cause transistor 29 to become saturated, that is, to become conductive. Current is then permitted to flow through the portion 23 of primary winding 21 of transformer 22, such current building up to .a maximum of E/Z, E :being the input voltage, and Z being the impedance of the series resistance and inductance of the primary circuit. When such maximum value of current has been reached, it momentarily approaches a constant level, causing the feedback volt age which is induced by changing primary current to become or approach 0, thereby causing the transistor to turn off or become non-conductive. As the transistor 39 turns oif, the decay of primary current causes a reverse feedback voltage to be induced in section 24 of the prirnary winding, thereby rapidly driving the transistor to its non-conductive condition. When transistor 29 has been turned off, the resistor 31 again repeats its above explained function, and causes oscillation in the generator circuit to continue.

As a result of the operation of the oscillator, a chopped direct current flows through section 23 of the primary 21 of the transformer 22. There is thus induced a voltage of alternating polarity in the secondary winding 41 of transformer 22. One end of the secondary winding 41 is connected to a rectifier 44 through a wire 42, the output of the rectifier being connected to a wire 43. The other end of the secondary winding is connected to a wire 45 which extends through the arming circuit to one terminal 60 of a first squib outlet. Close regulation of the voltage of the rectified direct current pulses delivered by rectifier 44 is secured by a circuit including a wire 46 connected to the output of rectifier 44, a resistor 47 interposed in wire 46, and a closely controlled spark gap 49 which is interposed between resistor 47 and wire 45. A condenser 50 is connected in shunt with the spark gap 49.

The spark gap 49 has a breakdown voltage which closely approximates the output voltage desired, in this instance such voltage being 2,000 volts. When the condenser 50 is charged to a voltage below the breakdown voltage of the spark gap 49, no discharge occurs across the gap. When the rectified voltage between wires 43 and 45 rises slightly, condenser 50 is charged to a value which causes spark gap 49 to fire, thereby discharging condenser 50 and momentarily shunting the secondary 41 of transformer 22 with resistor 47. The voltage between wires 43 and 45 then drops as condenser 50 is recharged. It can thus be seen that voltage regulation is 4 achieved by changing load impedance inversely with the voltage between wires 43 and 45.

The arming circuit includes two power-storing subcircuits connected in parallel to the rectified output of transformer 22. Connected to wire 43 is a first wire 51 which is connected to a rectifier 54. The output of the rectifier is connected to a resistor 55 which is interposed in a wire 56 leading to a first terminal 61 of a triggered spark gap device 62. Device 62 may have a construction similar to that disclosed in Linkroum U.S. Patent No. 3,187,- 215. Such spark gap device has three electrodes spaced to form two gaps of different lengths, the electrodes being sealed within a gas filled envelope. Connected in parallel across wires 45 and 56 are a resistor 59 and a storage condenser 57 for that branch of the arming circuit which powers the firing of squib 1. The corresponding portion of the arming circuit for supplying the power to fire squib 2 is smiliar. Such second sub-circuit includes a wire 52 connected to wire 43. The circuit elements in the second sub-circuit are designated by the same reference characters as those in the first sub-circuit but with an added prime. Wire 56' of the second sub-circuit leads to the first electrode 61 of a second triggered spark gap 62 through which power for firing squib 2 passes.

The second terminals to which the respective squibs are connected are designated 65 and 65'. Such terminals are connected to the second electrodes 63 and 63 through wires 64 and 64, respectively. It is to be noted that both leads to each squib are unconnected to ground; this prevents the possibility of any unintentional or undesired firing of the squibs by circulating ground currents.

In the illustrative embodiment a potential difference of 2,000 volts exists between wire 45 and each of wires 56 and 56. Condensers 57 and 57 are charged to approximately 2,000 volts through series resistors 55 and 55', respectively. Resistors 55 and 55 are provided in order to prevent a short circuit appearing in the tank circuit network, including condensers 57 and 57', from short circuiting the power supply. Resistors 55 and 55 may, for example, each have a resistance of 1 megohm. Because of the presence of resistors 55 and 55', a short circuit could appear in either of condensers 57 and 57', but the remaining operative condenser would reach its normal operating voltage. The resistors 59 and 59', connected in parallel to the storage condensers, provide for the discharging of the storage condensers when the arming circuit is deenergized. Resistors 59 and 59 each have a resistance which is appreciably greater than that of resistors 55 and 55, for example, on the order of 20 megohms.

The two trigger circuits 68 and 68', associated with the above described arming circuit, are identical in construction and manner of operation. Consequently, only circuit 68, which triggers the spark gap device 62 for the firing of squib 1, need be described in detail.

Circuit 68 has an input terminal 66 which is adapted to be connected to the output of a programmer. A wire 67 leads from terminal 66 to :a filter 69 which passes a direct current signal having a predetermined amplitude and minimum duration. In all illustrative embodiment, for example, filter 69 is so constructed and arranged that it passes effective triggering signals only when the signal received at terminal 66 has an amplitude of at least one ampere and a duration of at least 5 milliseconds. Filter 69 includes a series connected choke coil 70. A first condenser 71 is connected between wire 67 and ground, and a second condenser 72 is connected between the output wire 77 from the choke coil and ground. Filter 69 attenuates any spurious signals within the network before they reach the primary of step-up transformer 79, and also prevents any internally generated spurious noise from feeding back into the programmer. The coded signal required at the input of the described illustrative filter 69 is a positive square wave pulse of 271-3 volts amplitude, and 5 milliseconds duration.

Wire 77 is connected to one end of the primary wind ing 81 of the transformer 79, there being a resistor 74 interposed in such wire. The other end of winding 81 is connected to ground through wire 76. A diode 75 protects winding 81 from operation in response to signals of the wrong polarity. Diode 75 also prevents the spark gap 62 from being fired by low level signals which, when interrupted, might induce sutficient voltage to fire such spark gap.

Step-up transformer 79 has a secondary winding 82 and a core 80 which are magnetically linked with windings 81 and 82. The transformer 79 in the illustrative embodiment steps up the received triggering pulses so that the lead wires 83 and 86 from the secondary winding are at a potential difference of approximately 1,500 volts. A storage condenser 89, connected across wires 83 and 86, is charged to 1,500 volts upon the reception at the primary winding 81 of a coded pulse of the above described character. Connected to wire 86 beyond condenser 89 is a control gap 87, the other electrode of the gap being connected to a wire 84. Connected across wire 83 and wire 84 is a condenser 88. Wire 84 is connected to a third electrode 85 of spark gap device 62, the wire 83 being connected to electrode 63 of such spark gap through wire 64. Device 62 is so constructed that the breakdown voltage of the triggering gap 63, 85 is markedly less than the breakdown voltage of the gap 61, 63. The breakdown voltage of gap 61, 63 is substantially above 2,000 volts, and the breakdown voltage of gap 63, 85 is substantially below 1,800 volts.

When a cod-ed pulse has caused wires 83 and 86 to assume an increasing potential difference, condenser 89 becomes progressively charged. When condenser 89 has become charged to a sufficiently high potential, control gap 87 breaks down. The resulting surge of current charges condenser 88. When the voltage of the charge on condenser 88 becomes high enough, there ensues a breakdown of triggering gap 63, 85. Thereupon, the gas between electrodes 61 and 63 is ionized causing a discharge to occur across the latter gap so that storage condenser 57 of the arming circuit may discharge its energy to the output terminals 60, 65 to which squib 1 is connected. The arming circuit of the unit is quickly restored to a condition in which the storage condensers 57 and 57' are charged, so that the unit is again ready for operation, assuming that it remains on a stage of the missile which has not been separated.

Condenser 89 and control gap 87 may be omitted, if desired, wire 86 being connected directly to wire 84. It is preferred to employ elements 87 and 89 in the manner shown, however, since their use provides a more nearly instantaneous ionization of gap 63, 85, upon the reception of the proper signal by the triggering circuit, be cause the front of the pulse at electrode 85 provided by the described circuit is steeper than it is when elements 87 and 89 are omitted.

The firing circuit or set shown in FIG. 2 includes a number of sub-circuits and circuit elements which are similar to those above described in connection with the circuit of FIG. 1. Elements which are the same as those in the circuit of FIG. 1 are designated by the same reference characters in FIG. 2. In general the circuit of FIG. 2 differs from that of FIG. 1 by the use of a firing network which has a charging circuit powered by the arming circuit, and by the use of cascade connected triggering devices in the trigger circuit. Such triggering devices, when operated, release energy stored in the charging circuit, the thus released energy being fed to the triggering spark gap so as to initiate discharge of the storage condenser in the arming circuit to the exploding bridge Wire device. Such arrangement makes it possible, in an illustrative circuit in accordance with FIG. 2, to reduce the curent value of the coded triggering signal to less than milliamperes.

Turning now to FIG. 2, it will be seen that the arming circuit 10' thereof includes a pulse generator which is the same as that of FIG. 1. The coil 21 of such pulse generator forms the primary of a power transformer 90 having a core 91 and a secondary winding 92. Connected between the lead wires 42 and 45 from the ends of secondary winding 92, and beyond a first rectifier 44 is a voltage regulating circuit, including resistor 47, spark gap 49, and condenser 50, which is the same as that in FIG. 1. Connected in parallel to wire 43-, beyond rectifier 44, are two rectifying and energy storing sub-circuits which include storage condensers 57 and 57', respectively. An output wire 94 is connected to the first of such sub-circuits; an output wire 94' is connected to the second such sub-circuit. The second lead wire 45 is connected to-a common lead wire 106 which is connected to the sub-circuits, as shown, and to one terminal 107 and 107, respectively, of the outlets to which the squibs are connected. In the illustrative embodiments, the potential difference between wires 45 and 94 is 2,000 volts when the arming circuit is in operative condition.

The two firing networks 110 and 111 associated with arming circuit 10' for firing squib 1 and squib 2, respectively, are identical. Consequently, the same reference characters employed in identifying elements in network 110 are used in connection with network 111 but with an added prime. Firing network 110 has an input terminal 66 to which a discriminating filter 69 is connected. The output terminal of filter 69 is connected to a wire 112 which has series connected resistors 114 and 115 interposed therein, resistor 114 being variable, as indicated. Beyond resistor 115 such wire, there designated 120, is

connected to the emitter 121 of a unijunction transistor 122. Wire is connected to ground between resistor 115 and emitter 121 by a wire 119 which has a resistor 116 and a condenser 117 interposed in series therein. The output end of filter 69 is connected to the base 2, designated 126, of transistor 122 by a wire 124 which has a resistor 125 interposed therein. The base 1 of transistor 122, designated 127, is connected to one end of the primary winding 129 of a low voltage isolating transformer 130. The other end of winding 129 is connected to ground through wire 131.

Tnansformer 130 has a secondary winding 132, one end of which is connected to the cathode of a silicon controlled rectifier 137 by a wire 139. The other end of winding 132 is connected by a wire 135 to the gate 136 of the rectifier 137. A diode 134 is interposed in wire 135, as shown. The anode 141 of rectifier 137 is connected by a wire 142 to a charging circuit which receives its power from the arming circuit.

An intermediate tap 144 in the secondary 92 of transformer 90 is connected to two similar charging circuits connected in parallel by wires 145 and 145'. The charging circuit fed by wire 145 has a diode 146 and a resistor 147 connected in series between wires 145 and 142. Connected in parallel across wires 45 and 142 are a resistor 150 and a storage condenser 149. The tap 144 is disposed so that when the arming circuit is energized there is a potential difference of 100 volts between wires 45 and 142. The energy stored in condenser 149 is released through silicon controlled rectifier 137 when such rectifier has been rendered conductive upon the reception of a proper coded signal by the firing network, as Will be explained below.

The cathode 140 of rectifier 137 is connected to one end of the primary winding 151 of a step-up transformer 152. The other end of winding 151 is connected by a wire 154 to Wire 106 which is connected to Wire 45 and thence to one terminal of condenser 149. The other terminal of the condenser is connected through wire 142 to the anode 141 of rectifier 137 to complete a condenser discharge circuit through primary winding 151. The transformer 152 has a secondary winding 155, one end of which is connected to wire 94 which, in turn, is connected to a first electrode 95 of a triggered control gap 96 which is similar to the element 62 employed in the circuit of,

FIG. 1. The other end of winding 155 is connected by a wire 156 to a second electrode 157 of device 96. A third electrode, designated 97, of device 96 is connected to the second outlet terminal 99 to which squib 1 is connected. A third storage condenser 159 is connected across the secondary winding 155 of transformer 152. A wire 184 is connected between wire 142 and ground through a condenser 185. A diode 182 is connected between wire 184 and the end of primary 151 of transformer 152 which is connected to cathode 140 of rectifier 137.

The above described firing network functions as follows: In the described illustrative embodiment, the circuit 110 accepts an input signal having a square voltage wave of 2713 volts amplitude and a 0.1 second duration. After a delay of 80 milliseconds following the reception of such input signal, a pulse is produced at the secondary 132 of the transformer 130. This pulse turns silicon controlled rectifier 137 on, which allows condenser 149, charged to 100 volts, to discharge into the primary of transformer 152. This energy is transformed by transformer 152 to produce a high voltage pulse, on the order of 750 volts, at the secondary 155 of such transformer. This high voltage pulse produces a spark discharge in spark gap device 96 between electrodes 95 and 157 thereof which initiates full spark gap ionization and produces a low impedance path for condenser 57, which has been charged to 2,000 volts, to discharge into squib 1. In somewhat more detail, the sequence of events in the firing network is as follows: The firing signal when first applied will provide a voltage source through resistor 125 for the base 2 of unijunction transistor 122. This voltage produces a stand-off voltage for the emitter 121 of transistor 122, that is, the emitter to base 1 junction will have a reverse bias equal to that of the standoff voltage. T herefore, the emitter voltage must be raised above the standoff voltage before any current will flow from the emitter. The firing signal also provides a voltage source for resistors 114, 115, 116, and condenser 117. These resistors and the condenser form a resistance-capacitance (RC) network through which condenser 117 will be charged. When the charge on condenser 117 has been raised to the stand-off voltage, the emitter to base 1 junction of transistor 122 will become forward biased, and the emitter to base 1 junction will rapidly fall into a saturation region discharging the energy stored in condenser 117 to the primary 129 of transformer 130.

The time delay between the time of the firing signal application and the discharge of condenser 117 can be adjusted by varying resistor 114. In the illustrative circuit such time delivery may be, for example, 80 milliseconds. The pulse supplied to primary 129 and transformer 130 induces voltage in secondary 132 of such transformer to provide sufficient energy to trigger the rectifier 137. As noted, condenser 149 will have been charged to 100 volts. Rectifier 137 acts as an open switch until the gate 136 thereof is energized, thereby keeping condenser 149 from discharging into the primary 151 of step-up transformer 152. When the gate 136 of rectifier 137 is energized as described, the rectifier becomes saturated and acts as a shorting switch. Thus the condenser 149 will then discharge its stored energy through rectifier 137 to the primary 151 of transformer 152.

The surging of current through primary 151 induces a voltage in secondary 155 of transformer v152, thereby charging condenser 159. When the voltage to which condenser 159 is charged reaches the breakdown voltage of the gap 95, 157, there will be a spark discharge between the electrodes of such gap. Condenser 159 acts as an energy storage device .to provide follow-through current, once the trigger voltage has reached the ionization level. The triggering arc discharge initiates the ionization of the gas between electrodes 95 and 97, thereby causing a sudden reduction of spark gap impedance from an effectively open to an effectively short circuit. This then places condenser 57, charged to 2,000 volts, directly across the terminals 99 and 107, thus firing the exploding bridge wire device connected thereto.

The preferred embodiment of circuit in accordance with FIG. 2 incorporates a number of safety factors and features to improve its reliability and to prevent any unintentional or undesired firing of the squib. The diode 134 is employed to prevent any possible reverse bias voltage from destroying the silicon controlled rectifier 137. The diode 182 likewise protects rectifier 137 against reverse voltage. Resistors [147 and 147 in the charging circuit have the same function as resistors 55 and 55. Thus if one of the condensers 149 and .149 should become shortcircuited, the respective one of the resistances 147 and 147' permits the other charging circuit branch to remain operative. The condenser 185 shorts out transients which might otherwise reach circuit 110, for example, those arising in circuit 111. The stand-off voltage of transistor 122 and the voltage source for charging condenser 117 are both obtained from the firing signal. This insures that when no firing signal is present there will be no way for the transistor 122 to cause any unintentional or undesired firing of the squib. As an added safety factor, in the preferred circuit, the step-up transformer 152 supplies energy in marked excess of that required to trigger the spark gap device 96, for example, on the order of four times as much energy as that required to cause such triggering action.

In a preferred embodiment of the circuit of FIG. 2 there are employed circuit elements having the following values: Adjustable resistor 114 has a resistance of 0-100K ohms; resistor 115 has a resistance of 50,000 ohms; resistor 116 has a resistance of 100 ohms; resistor has a resistance of 470 ohms; and resistor 147 has a resistance of 6.8K ohms. Condensers 57, 117, and 149 have capacitances of 1 mfd., 2 mfd., and 5 mfd., respectively.

The third illustrative embodiment of firing circuit or set in accordance with the invention is shown in FIG. 3. In general the circuit of FIG. 3 differs from that of FIG. 2 by the design of the firing network to make it such as to accept only chopped D.C. pulses and to be inoperative upon the application of a steady state D.C. signal. The circuit of FIG. 3 is therefore rendered safe against a positive failure, that is, an unintentional firing resulting from a steady state 27:3 volts D.C. signal at the input to the firing circuit, due to a malfunction of the missile distribution system. Parts in the circuit shown in FIG. 3 which are the same as those in FIG. 2 are designated by the same reference characters, and are not discussed below in any detail, except where necessary to explain the manner of connection and functioning of the parts added in FIG. 3.

The circuit of FIG. 3 includes an arming circuit and two similar networks 161 and 162 for the firing of squibs or exploding bridge Wire devices Nos. 1 and 2, respectively. The arming circuit includes two charging circuits connected in parallel and deriving their energy from the power transformer 90. As in the circuit of FIG. 2, the storage condenser in the charging circuit discharges through a silicon controlled rectifier 137, thus energizing transformer 152 to trigger the spark gap device 96.

The parts added in the firing circuit 161 are as follows: Between the output of filter 69 and the input wire 112 connected to variable resistor 114 there are interposed in that order series connected resistor i170, condenser 179, and diode 180. A wire 171 is connected between resistor and condenser 179, wire 171 being connected to a zener diode 172, as shown. The other terminal of the zener diode is connected to ground through wire 174. A wire 177 is connected between condenser 179 and diode 180. Wire 177 is connected to a diode 1176, the other end of such diode being connected to ground by a wire 175. Circuit 161 further differs from circuit 110 of FIG. 2 by incorporating a resistor 181 connected between ground and the wire 120 connected to the emitter 121 of transistor 122.

=In a preferred embodiment of circuit in accordance with FIG. 3, the above described added circuit elements have the following values: Resistor 170 has a resistance of 1,500 ohms. Condenser 179 has a capacity of 1 mfd. Resistor 181 has a resistance of 1 megohm.

The circuit of FIG. 3 further differs from that of FIG. 2 as to the source of the stand-off voltage for the base 2 electrode 126 of unijunction transistor 122. Thus in the circuit of FIG. 3 the electrode 126 of the transistor is connected to primary lead wire 19 of the arming circuit through serially connected wire 164, resistor 165, and a wire 167 in which there is interposed a resistor .169. The stand-off voltage for the transistor 1 22 is thus derived from a source which is independent of the signal. To remove any adverse effects of variations in the voltage supplied to arming circuit 160, a Zener diode 166 is connected between wire i167 and ground, as shown. Diode 166 maintains a constant voltage source for the base 2 voltage of transistor 122. Zener diode 1'72 insures that the voltage of the trigger input pulse does not exceed a predetermined value, for example, 20 volts. Diode 180 is a blocking diode to keep condenser 117 from discharging into condenser 179 during the off time of the signal pulse. Resistor 1181 provides for the slow draining of power from condenser 117 during periods of disuse of the firing network. [Diode 1 76 insures that condenser -179 will discharge during the intervals between the signal pulses. As with the circuit of FIG. 2, the delay time of the firing network can be controlled by adjusting resistor i114. The above described circuit of FIG. 3, in the described preferred embodiment thereof, accepts a code-d signal having a repetition rate of '70 cycles per second with an approximate on to off time of '2 to 1. It is to be understood, however, that such rate is not critical, and is capable of wide variation depending upon the design of the circuit and the manner in which the circuit is applied.

Although only a limited number of embodiments of the invention have been illustrated in the accompanying drawings and described in the foregonig specification, it is to be especially understood that various changes, such as in the relative dimensions of the parts, materials used,

and the like, as well as the suggested manner of use of the apparatus of the invention, may be made therein without departing from the spirit and scope of the invention as will now be apparent to those skilled in the art.

What is claimed is:

1. In electrical apparatus for generating current pulses of spark intensity, the combination of an arming circuit and a triggering circuit controlling the discharge of the arming circuit, the arming circuit comprising a generator of direct current pulses, a first storage condenser connected to be charged by the said pulses in the arming circuit substantially to the potential of said pulses, a spark gap device, having a first, main discharge gap with a breakdown voltage value appreciably greater than the potential of said pulses, and a second triggering gap of smaller breakdown potential than the first gap and located in proximity to the first gap, and a discharge circuit connected to the main gap of the spark gap device and adapted to be connected to a load device operated by a current pulse of spark intensity, the triggering circuit being adapted to be connected to a source of current pulses and comprising a discriminating filter which passes only pulses of a predetermined character, a pulse voltage step-up transformer having a primary Winding and a secondary winding, the primary winding being connected to be fed by filtered pulses of the triggering circuit, a second storage condenser connected to be charged by the secondary winding of the pulse transformer, and a circuit connecting the second storage condenser to the triggering gap of the spark gap device, the second storage condenser being adapted to be charged to a potential higher than the breakdown voltage of the triggering gap and thereafter to discharge through the triggering gap to initi- 10 ate discharge of the first storage condenser through the main gap of the spark discharge device.

2. Electrical apparatus as claimed in claim 1, comprising means to control the voltage of the pulses produced by the generator so that it does not exceed a predetermined maximum value.

3. Electrical apparatus as claimed in claim 1, wherein the filter passes a triggering signal applied to the triggering circuit which is a current pulse having at least a predetermined amperage and is of at least a predetermined duration.

4. Electrical apparatus as claimed in claim 1, wherein the output of the pulse step-up transformer is connected to the triggering gap of the spark gap device, and the second storage condenser is connected across the secondary winding of the pulse step-up transformer.

5. Electrical apparatus as claimed in claim 1, wherein the triggering circuit includes a sub-circuit connected between the output of the filter and the primary winding of the pulse step-up transformer, said sub-circuit comprising a first switching device connected to the output of the filter, means to maintain the first switching device in off condition in the absence of a triggering pulse from the filter, and to place the first switching device in on condition upon the reception of a triggering signal from the filter, a second switching device connected to the output of the first switching device, a third storage condenser connected to the second switching device, means to charge the third storage condenser from a source of power separate from the triggering circuit, the output of the second switching device being connected to the primary winding of the pulse step-up transformer, the second switching device being in off condition in the absence of a pulse from the first switching device and being rendered conductive upon the reception of a pulse from the first switching device, whereby to discharge the third storage condenser into the primary winding of the pulse step-up transformer.

6. Electrical apparatus as claimed in claim 5, wherein the first switching device is a transistor having an emitter to which the output of the filter is connected, and comprising circuit means for producing a stand-off voltage for the emitter of the transistor, and time delay means to raise the voltage of the emitter above said stand-off voltage of the emitter, whereby to render the transistor conductive.

7. Electrical apparatus as claimed in claim 5, wherein the second switching device is a silicon controlled rectifier having an anode, a cathode, and a gate, the gate being connected to the output of the first switching device, the anode being connected to the third condenser, and the cathode being connected to the primary winding of the pulse step-up transformer, whereby the third condenser discharges into said primary winding when the silicon controlled rectifier is rendered conductive.

8. Electrical apparatus as claimed in claim 5, c0mpris ing an isolation transformer connected in circuit between the output of the first switching device and the control terminal of the second switching device.

9. Electrical apparatus as claimed in claim 6, wherein the triggering circuit is adapted to receive and respond solely to current pulses having a predetermined minimum amperage, a predetermined pulse duration, a predetermined rate of pulse repetition, and a predetermined total input of triggering power, wherein the filter passes only a predetermined range of pulse frequencies, and comprising a discriminator circuit in series with the filter for blocking the passage of uninterrupted direct current and of current pulses having a polarity opposite from the desired polarity, said discriminator circuit comprising a condenser and a first diode in series with the triggering circuit, a zener diode and a further diode connected, between ground, and respectively, between the filter and the condenser of the discriminator circuit, and between such condenser and the first diode.

10. Electrical apparatus comprising a source of electrical energy, a rectifier, a storage condenser connected to said source to be charged thereby through said rectifier, a resistor connected in shunt with said storage condenser, and means for limiting the maximum voltage of the charge applied to said condenser by said source, said means comprising a second rectifier, a second resistor and a spark gap connected in series across said source and a second condenser connected in parallel with said spark gap, said first-named rectifier and said storage condenser being connected in parallel with said series connected second resistor and spark gap.

11. Electrical apparatus as defined in claim wherein said spark gap has a breakdown voltage closely approximating said maximum voltage.

12. Electrical apparatus comprising a source of electrical energy, a storage condenser connected to be charged by said source, a load circuit connected across said condenser including a spark gap having a normal spark over voltage greater than the maximum charge applied to said condenser by said source, means for ionizing said gap to render the same conductive to the charge on said storage condenser, said means including a triggering condenser connected across a triggering gap between one electrode of said gap and a triggering electrode adjacent said one electrode, and means for charging said triggering condenser to the spark-over voltage of said triggering gap, said last-named means comprising a transformer having a secondary winding connected across said triggering condenser and a primary Winding, a third condenser connected to be charged by said first-named source, a silicon controlled rectifier having its normally non-conductive anode-cathode path connected in series with said primary winding across said third condenser, and means for rendering said rectifier conductive to the charge on said third condenser.

13. Electrical apparatus as defined in claim 12 wherein the means for rendering the rectifier conductive comprises a second transformer having a secondary Winding connected across the control gate and cathode terminals of said rectifier and a primary winding, and means for energizing the latter.

14. Electrical apparatus as defined in claim 13 wherein the means for energizing the primary Winding of said second transformer comprises a normally non-conductive unijunction transistor having the base one terminal thereof connected to said last-named primary winding, means for applying a voltage to the base two terminal of said transistor, an RC circuit comprising a resistor and condenser connected in series with each other and in parallel with the emitter-base one path of the transistor, and means for supplying electrical energy to charge said lastnamed condenser and render said transistor conductive.

References Cited by the Examiner UNITED STATES PATENTS 2,071,958 2/1937 Watrous 315-24l X 2,696,587 6/ 1954 Stratton 32322 2,804,547 8/ 1957 Mortimer 331-112 2,820,179 1/1958 Crowther 315245 X 2,930,989 3/1960 Krieger 3311 12 2,938,147 5/1960 Rose 3 l5l60 2,942,152 6/1960 Stoelting 315-238 2,967,975 1/1961 Hartman 315-241 3,041,500 6/1962 Vlodrop 315238 X 3,049,642 8/1962 Quinn 315-241 JAMES W. LAWRENCE, Primary Examiner.

GEORGE N. WESTBY, Examiner.

C. R. CAMPBELL, Assistant Examiner. 

1. IN ELECTRICAL APPARATUS FOR GENERATING CURRENT PULSES OF SPARK INTENSITY, THE COMBINATION OF AN ARMING CIRCUIT AND A TRIGGERING CIRCUIT CONTROLLING THE DISCHARGE OF THE ARMING CIRCUIT, THE ARMING CIRCUIT COMPRISING A GENERATOR OF DIRECT CURRENT PULSES, A FIRST STORAGE CONDENSER CONNECTED TO BE CHARGED BY THE SAID PULSES IN THE ARMING CIRCUIT SUBSTANTIALLY TO THE POTENTIAL OF SAID PULSES, A SPARK GAP DEVICE, HAVING A FIRST, MAIN DISCHARGE GAP WITH A BREAKDOWN VOLTAGE VALUE APPRECIABLY GREATER THAN THE POTENTIAL OF SAID PULSES, AND A SECOND TRIGGERING GAP OF SMALLER BREAKDOWN POTENTIAL THAN THE FIRST GAP AND LOCATED IN PROXIMITY TO THE FIRST GAP, AND A DISCHARGE CIRCUIT CONNECTED TO THE MAIN GAP OF THE SPARK GAP DEVICE AND ADAPTED TO BE CONNECTED TO A LOAD DEVICE OPERATED BY A CURRENT PULSE OF SPARK INTENSITY, THE TRIGGERING CIRCUIT BEING ADAPTED TO BE CONNECTED TO A SOURCE OF CURRENT PULSES AND COMPRISING A DISCRIMINATING FILTER WHICH PASSES ONLY PULSES OF A PREDETERMINED CHARACTER, A PULSE VOLTAGE STEP-UP TRANSFORMER HAVING A PRIMARY WINDING AND A SECONDARY WINDING, THE PRIMARY WINDING BEING CONNECTED TO BE FED BY FILTERED PULSES OF THE TRIGGERING CIRCUIT, A SECOND STORAGE CONDENSER CONNECTED TO BE CHARGED BY THE SECONDARY WINDING OF THE PULSE TRANSFORMER, AND A CIRCUIT CONNECTING THE SECOND STORAGE CONDENSER TO THE TRIGGERING GAP OF THE SPARK GAP DEVICE, THE SECOND STORAGE CONDENSER BEING ADAPTED TO BE CHARGED TO A POTENTIAL HIGHER THAN THE BREAKDOWN VOLTAGE OF THE TRIGGERING GAP AND THEREAFTER TO DISCHARGE THROUGH THE TRIGGERING GAP TO INITIATE DISCHARGE OF THE FIRST STORAGE CONDENSER THROUGH THE MAIN GAP OF THE SPARK DISCHARGE DEVICE. 